Lateral deformation under the side slopes of Piled embankments

Piled embankments are used widely for the construction of roads and rails infrastructure over soft and/or compressible soils. The design of piled embankments is a complex soil - structure interaction problem and is not yet fully understood. Traditional design methods, such as BS 8006(1995), assume that any lateral trust is carried by the geosynthetic reinforcement placed at the base of the embankment directly over the pile caps. At the extremities of the embankment both horizontal equilibrium and strain compatibility between the different components, the embankment fill, the geosynthetic reinforcement, the pile group and the soft soil, must be achieved (Love & Milligan 2003). This paper examines the horizontal and vertical deformation, axial tension developed in the geosynthetic reinforcement and bending moment developed in the pile for a range of complex embankment geometries. The finite element analysis using Plaxis 2D indicates for the geometries examined, that both the horizontal and vertical deformation under the side slope of the embankment can be significant. An increase in the reinforcement tension under the side slope was also observed. The maximum bending moment was found in the outer most rows of piles, while the piles near the center line had a reasonably small moment. The deformations, axial tension and bending moment in the piles were found to be a function of the embankment geometry (height, steepness of side slope and pile spacing) and stiffness of the foundation soil.